generate-sample-pdfs-with-reportlab.md

Generate Sample PDFs With ReportLab

The reportlab package has a pdfgen module that provides a Canvas API for programmatically constructing a PDF.

I recently needed the most basic use of this to quickly construct a sample PDF that I could use as I experimented with different qpdf commands. I wanted to generate a 10-page PDF where each page included a large font number in the center. This way I could clearly see what was the first, second, third, and so on pages. Then I could quickly verify that the qpdf manipulations I was doing were working as expected.

I was able to do this without any setup or install. Using a uv one-liner (does a 10-line heredoc count as a one-liner?), I generated a PDF with some basic canvas rendering on each page.

❯ uv run --with reportlab python - <<'EOF'
from reportlab.pdfgen import canvas
N, W, H = 10, 612, 792
c = canvas.Canvas("test.pdf", pagesize=(W, H))
for i in range(1, N + 1):
    c.setFont("Helvetica-Bold", 220)
    c.drawCentredString(W / 2, H / 2 - 80, str(i))
    c.setFont("Helvetica", 28)
    c.drawCentredString(W / 2, 100, f"page {i} of {N}")
    c.showPage()
c.save()
EOF

The --with makes the reportlab package available to the command being run. The command being run is python which evaluates that block of heredoc text.

Within the heredoc, I import canvas from the reportlab package that has been made available. I then create an in-memory PDF of a standard size. Then for-loop 10 times to build each page of the PDF with a big number in the middle and a smaller page x of N lower down on the page. Finally, I save the PDF which writes it to the directory I executed this whole command from.

I had Claude help with the canvas API, however there are some decent reportlab.pdfgen docs here.